OpenAPITools/openapi-generator · error · IllegalArgumentException

Invalid file naming '{}'. Must be 'camelCase' or 'kebab-case

Error message

Invalid file naming '{}'. Must be 'camelCase' or 'kebab-case'

What it means

fileNaming for the Angular generator accepts exactly 'camelCase' or 'kebab-case' (unlike some other TypeScript generators it has no PascalCase support). An unsupported value throws during option processing.

Source

Thrown at modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptAngularClientCodegen.java:727

            String values = Stream.of(QUERY_PARAM_OBJECT_FORMAT_TYPE.values())
                    .map(value -> "'" + value.name() + "'")
                    .collect(Collectors.joining(", "));

            String msg = String.format(Locale.ROOT, "Invalid query param object format '%s'. Must be one of %s.", format, values);
            throw new IllegalArgumentException(msg);
        }
    }

    /**
     * Set the file naming type.
     *
     * @param fileNaming the file naming to use
     */
    private void setFileNaming(String fileNaming) {
        if ("camelCase".equals(fileNaming) || "kebab-case".equals(fileNaming)) {
            this.fileNaming = fileNaming;
        } else {
            throw new IllegalArgumentException("Invalid file naming '" +
                    fileNaming + "'. Must be 'camelCase' or 'kebab-case'");
        }
    }

    /**
     * Converts the original name according to the current <code>fileNaming</code> strategy.
     *
     * @param originalName the original name to transform
     * @return the transformed name
     */
    private String convertUsingFileNamingConvention(String originalName) {
        String name = this.removeModelPrefixSuffix(originalName);
        if ("kebab-case".equals(fileNaming)) {
            name = dashize(underscore(name));
        } else {
            name = camelize(name, LOWERCASE_FIRST_LETTER);
        }
        return name;

View on GitHub (pinned to fcec517be3)

Solutions

1. Set fileNaming to 'camelCase' or 'kebab-case'.
2. If PascalCase file names are required, use a generator that supports it (e.g. typescript-fetch) or post-process the output.

Example fix

# before
openapi-generator generate -g typescript-angular -i api.yaml -DfileNaming=PascalCase

# after
openapi-generator generate -g typescript-angular -i api.yaml -DfileNaming=kebab-case

// node: Angular accepts only these two file naming values
const NAMING = ['camelCase', 'kebab-case'];
if (opts.fileNaming && !NAMING.includes(opts.fileNaming))
  throw new Error(`fileNaming must be one of ${NAMING.join('|')}`);

const isAngularFileNaming = (v: string): v is 'camelCase' | 'kebab-case' =>
  v === 'camelCase' || v === 'kebab-case';

// Java
try { new DefaultGenerator().opts(input).generate(); }
catch (IllegalArgumentException e) {
    // unsupported naming value: switch to camelCase/kebab-case and rerun
}

When it happens

Trigger: -DfileNaming=PascalCase, snake_case, or any string other than the two accepted values.

Common situations: Copying fileNaming options from the typescript-fetch generator (which supports PascalCase) into an Angular job; assuming snake_case is available because it is common in other tools.

Related errors

• %s file suffix only allows '.', '-' and alphanumeric charact
• %s class prefix only allows alphanumeric characters.
• %s class suffix only allows alphanumeric characters.
• Invalid ngVersion: " + ngVersion + ". Only Angular v9+ is su
• Invalid query param object format '%s'. Must be one of %s.

AI-assisted analysis of OpenAPITools/openapi-generator@fcec517be3 (2026-08-22). Data as JSON: /api/errors/75ded544aab2297b. Report an issue: GitHub.